RE: [wxhaskell-users] wxhaskell vs. HToolkit

[Daan L. <daa...@xs...>]

Hi Per,

> I have lately experimented with both wxhaskell and HToolkit. 
> I'm a bit  confused, they seems very similiar in style and have common

> implementors (Daan Leijen).  

History:

At the beginning of 2003, I was disappointed with the current state
of affairs regarding GUI's for Haskell. A most promising project
was the HToolkit library by Krasimir Angelov. He started this project
to make a portable successor of the objectIO library.

He created a low-level C interface for programming GUI's. He 
implemented this interface for both Windows and GTK -- getting
a somewhat portable way to program GUI's. HToolkit was a bit
monolithic at that time and I separated out the low-level interface
(Port) and designed a higher level interface (GIO).

Although I was very enthousiastic to begin with, I slowly became
aware of the drawbacks of this approach. In my opinion, it will
be too hard to maintain such a library for multiple platforms -- 
slowly the task will grow bigger and bigger, and bugs just kept
creeping up. Furthermore, I realized that it is probably also
too much work to support the amount of features necessary 
for "real" applications. I got more and more confirmed in my
doubts when I studied other portable GUI libraries -- almost all
have died a slow and lingering death due to unsupported features,
platforms, and bugs -- even rather nicely designed and technologically
advanced libraries.  

So, in the end I concluded that designing, implementing, and
*maintaining*
such library will be too hard for a small community like that of
Haskell,
and I abandoned the project (although I still believe it is a nice
and cleanly designed library)

The right way of doing a portable library for Haskell, is to build on 
the work of others! So I used the wxWindows library as the basis to
build a portable GUI library for Haskell. wxWindows is free, portable
across many platforms (windows,macOSX,GTK,X11,...) and has a large
and active user community (top 25 of sourceforge, over 1 million
downloads). 
Furthermore, rather serious applications have been written in it, 
including the latest AOL communicator and Mojoworld. 

The good part is now that we don't have to do anything (well, almost:-)
to run on different platforms -- that is all done by the wxWindows
community.
Furthermore, the interface is generated automatically, so it is easy
to follow new versions and to maintain the library. And we are not the
only ones to see these advantages, wxPython is higly popular and many
other bindings are there: wxEiffel, wx.NET, wxJScript, wxLUA, etc.

wxWindows is also fairly comprehensive -- this makes it easy to support
new features: just over the weekend there is support for portable ODBC 
and the OpenGL canvas (will be included in the next release).
It saves a *lot* of work when all the hard parts have already been done
by others :-)

There are also drawbacks: wxWindows is not as "clean" as I would have 
liked it to be, it written in C++, the library is rather large etc. But
I don't think these drawbacks are serious enough in the light of the
advantages.


> I have also read that the haskell community  has decided that 
> the "common GUI" project, which I suppose HToolkit is an 
> implementation of, is no longer officially supported as a project for
obtaining 
> a standard GUI library for haskell, but that wxhaskell instead is the 
> preferred library.

Opinion:

This is a "sensitive" subject :-).  I would say that the
"common GUI" interface is not abandoned. It still makes sense to define
a kind of standard medium level interface that is somewhat 
standardized. However, I believe that it is too hard at this moment
to define such a thing -- besides technical challenges with regard to 
types, it is also unclear how the interfaces should look like. There is
no
well defined goal and I think that is because there are just not many
real GUI programs written in Haskell (except maybe for Programmatica?)

> What will be the practical implications of that wxhaskell is 
> officially supported by the haskell community and that HToolkit is
not? 

Current:

It is a rather unfortunate situation that in this small community
there are now two libraries that try to do the same thing :-( 
I don't know what to do about this, and maybe we should just leave
it as it is (although I would love to have Krasimir as a co-developer,
he is an excellent programmer :-).

I hope this answers some of your questions,
and that it puts things into perspective,

All the best,
 Daan Leijen.

 
> Regards
> Per
> 
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> 
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